Retention of filter elements

ABSTRACT

A filtration apparatus comprises a plurality of filtration sections such as ( 12, 13 ), each covered on both opposed faces by a filter cloth ( 14 ). Each filter cloth ( 14 ) is formed with a compressible edge bead ( 26 ) which is received in a corresponding groove ( 22-25 ) in a member ( 20 ) which extends between the sections ( 12, 13 ). The grooves each have an orifice for reception of the edge beads which is less than the diameter of the groove. Member ( 20 ) has a hollow core ( 21 ) to receive a sector dividing stem ( 17 ) to pass along and reinforce the member ( 20 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the retention of filter elements, principallyin the art of vertically rotating disc filters, each composed of aplurality of filter segments.

2. Related Art

Examples of such filters are described in U.S. Pat. No. 3,283,906 toCrane and U.S. Pat. No. 3,331,512 to Vore. Each segment comprises agenerally wedge shaped hollow plate with perforated surface webs,covered on each side with an appropriate filter cloth. Liquid is drawninto the cavities within the plate, through the filter cloths by suctionachieved by known means, as the respective sector is dipped into anunfiltered slurry or other prefiltrate. Particles above the retentionthreshold of the filter cloths are retained by the filter cloths, whilstliquid and fine particles below the threshold pass into the interior ofthe segment plate, and are pumped therefrom. On emergence from the bathof unfiltered slurry, to be exposed to the air, the cake of retainedparticles on the filter cloth can be removed by scrapers or other knownmeans.

Disc filters of this kind are commonly used in filtration of mineralssuch as coal dust, ores or the like. Each filter disc may comprise 8 to12 sectors, each from 0.4 to 1.8 m in height, and two or three skilledworkers may be needed to fit and remove each sector, which in knownfilters is required in order to remove old filter cloths, and fitreplacements. A complete installation may comprise up to 200 filterwheels or more and the operation of changing filter cloths may takeseveral days, as each sector may occupy 2-3 workers to remove, dress andre-fit so that each wheel may represent a full day's work for each teamemployed.

SUMMARY OF THE INVENTION

An object of the invention is to provide means for retention of filtercloths on the segments of a disc filter, which will enable the filtercloths to be removed and replaced quickly and easily, and withoutremoval of the segment from the wheel.

According to the invention, in a filtration apparatus, wherein theapparatus comprises two or more adjacent filtration sections, there isprovided means for retaining at least one filter element over eachfiltration section, comprising an elongate member extending betweenadjacent filtration sections, said elongate member having respectivegrooves therein to receive an edge bead provided in each filter element.

Preferably the bead, or at least the lips of the grooves are of flexiblematerial, to enable the bead to be pushed into and pulled from thegrooves.

The filtration apparatus is preferably a vertical disc filter of thekind described above, but may be a horizontal pan filter, comprising asimilar assembly of a plurality of segments, or a drum filter comprisinga plurality of part cylindrical panels.

In the case of a disc filter, the elongate member may have a hollowcore, to enable a sector dividing stem to pass along the elongatemember. These stems provide mechanical strength to the structure of thedisc.

In a preferred embodiment, the elongate member comprises an extrusion ofprofiled cross section of a hard plastics material, such aspolypropylene, polyethylene or polyamide or a blend of two or morethereof, or of a lightweight metal such as aluminium or an alloythereof. Two grooves may be provided at each side of the member toreceive the edges of two filter cloths, one on each face, of each of thesectors abutting the elongate member.

The bead on each filter cloth edge is preferably an elastomericextrusion, of e.g. natural or synthetic rubber or the like, which can bedeformed to be forced into the respective groove, or to be pulled outfrom it. The bead may be formed with flaps or rods between which an edgeof a filter cloth may be received, and secured for example by at leastone of stitching or welding. It is noted that the bead is preferablymade of a softer material than the elongate member.

The grooves of the elongate member are preferably circular in crosssection, set deeper than their radius, so that they present an orificeslit which is less than the diameter of the groove, thereby forcingcompression of the bead for insertion or withdrawal, and acting toretain the bead in normal use.

The invention also provides filtration apparatus comprising two or moreadjacent filtration sections. Each section being provided with one ormore filter elements, and retaining means for retaining the filterelements. The retaining means comprising an elongate member extendingbetween adjacent filtration sections. The elongate member having arespective groove therein for receiving an edge bead provided on eachfilter element.

BRIEF DESCRIPTION OF THE DRAWINGS

These together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout.

A preferred embodiment of the invention will now be described by way ofexample, with reference to the accompanying drawings, wherein:

FIG. 1 is a diagrammatic view of one segment of a vertical disc filterembodying the invention;

FIG. 1a is a detail of an edge cap;

FIG. 1b is a side view of a lock-down bar used to secure a filter clothnear the hub of the disc;

FIG. 2 is a detailed sectional view of an elongate member in placebetween two adjacent disc segments;

FIG. 3 is a sectional view of the edge of a filter cloth used in thefilter; and

FIG. 4 is a cross section of the elongate member.

DESCRIPTION OF THE INVENTION

Although only one preferred embodiment of the invention is explained indetail, it is to be understood that other embodiments are possible.Accordingly, it is not intended that the invention is to be limited inits scope to the details of construction and arrangement of componentsset forth in the following description or illustrated in the drawings.The invention is capable of other embodiments and of being practiced orcarried out in various ways. Also, in describing the preferredembodiment, specific terminology will be resorted to fro the sake ofclarity. It is to be understood that each specific term includes alltechnical equivalents which operate in a similar manner to accomplish asimilar purpose.

The disc segments are separated by generally radial sector stems 17which provide mechanical strength to the construction of the disc.

The radially outer edges of the segments are covered by rectangulartrough-shaped sector caps 18, which also clamp the outer edges of thefilter cloths 15, 16.

The radially inner edges of the filter cloths 15, 16 are secured by alock-down bar 19 on each face of the segment, secured by Tec screws. Thebar 19 can be easily secured and released, using a screwdriver.

The radially extending edges of each segment are separated by elongatedmembers 20, in the form of extrusions from e.g. polyamide. The members20 each have an axial passage 21, through which extends a respectivesector stem 17.

The member 20 is generally rectangular in shape and is situated betweenthe adjacent sector plates 14, 15 of adjacent segments, with the longerfaces in-abutment with the plates. The shorter faces of the member 21are each provided with a pair of circular cross sectioned grooves 22, 23in the upper face and 24, 25 in the lower face. Each groove opens with aslot which is narrower than the diameter of the groove. For example, thediameter of the groove is typically 9 mm, whilst the width of the slotis typically 4 mm.

Each groove 22, 23, 24, 25. receives an edge bead 26 on the edge of arespective filter cloth 15, 16. Each edge bead 26 is secured to thefilter cloth by means of flaps 27 between which the cloth is inserted,and secured by stitching 28.

The edge bead 26 is of a flexible or at least deformable syntheticmaterial, or a rubber or the like. The bead 26 is capable of beingdeformed to enter the slot of the respective groove, or to be pulled outfrom the groove.

In use, a disc filter is dressed by simply removing the respectivesector caps 18 to release the radially outer edges of the filter cloths,then the lock-down bars 19 are detached. The used filter cloths can thenbe removed by pulling the edge beads 26 from their respective grooves.in the elongate member 20. Replacement clean filter cloths are fitted bythe reverse procedure, that is pushing their edge beads 26 into thegrooves in the member 20, and then securing the lock-down bars 19 andthe sector caps 18.

Instead of requiring two or three workers over an hour, because thesector does not have to be disconnected, changing filter cloths on asegment can be carried out by one person in about 10 minutes.Consequently, dressing. a complete installation of 200 disc filters maytake about 400 man-hours, as opposed to 7200 man-hours approximately forthe prior art installation.

Existing installations may be modified to conform with the invention.

In a pan filter or a rotary drum filter, the elongate members would besolid with no passage through the middle.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and, accordingly, all suitable modifications and equivalentsmay be resorted to, falling within the scope of the invention.

What is claimed is:
 1. A filtration apparatus comprising a disc made upof a plurality of segments, said segments being separated by radiallyextending elongate members and each said segment comprising perforatedplates enclosing an interior volume, and a filter cloth each covering arespective face of said segment being formed having an integral edgebead, the improvement comprising said elongate members each including ahollow core to receive a reinforcing member and provided with pairs ofgrooves each receiving the edge bead on the edge of a respective filtercloth for retaining the edges of said filter cloths.
 2. The filtrationapparatus according to claim 1, wherein said lips of said grooves are offlexible material, to enable said bead to be pushed into and pulled fromsaid grooves.
 3. The filtration apparatus according to claim 1, whereinsaid elongate member comprises an extrusion of a profiled cross sectionof a relatively hard plastics material, and has two grooves provided ateach side of said member to receive said edges, and said edge beadscarried thereby, of two filter cloths, one on each face, of each of saidfiltration section abutting said elongate member.
 4. The filtrationapparatus according to claim 1, wherein said bead on each filter clothedge is an elastomeric extrusion which can be deformed to be forced intosaid respective groove.
 5. The filtration apparatus according to claim1, wherein said bead is formed with flaps between which an edge of afilter cloth is received, and secured by stitching, and is of a softermaterial than said elongate member.
 6. The filtration apparatusaccording to claim 1, wherein said grooves in said elongate member areof circular cross section and set deeper than their radius, so that theypresent an orifice which is less than a diameter of said groove.
 7. Thefiltration apparatus according to claim 1, wherein said elongate membercomprises an extrusion of a profiled cross section of a lightweightmetal, and has two grooves provided at each side of said member toreceive said edges, and said edge beads carried thereby, of two filtercloths, one on each face, of each of said filtration section abuttingsaid elongate member.
 8. The filtration apparatus according to claim 1,wherein said bead on each filter cloth edge is an elastomeric extrusionwhich can be deformed to be pulled out from the groove.
 9. Thefiltration apparatus according to claim 1, wherein said bead is formedwith flaps between which an edge of a filter cloth is received, andsecured by welding, and is of a softer material than said elongatemember.
 10. The filtration apparatus according to claim 1, wherein saidbead is formed with rods between which an edge of a filter cloth isreceived, and secured by stitching, and is of a softer material thansaid elongate member.
 11. The filtration apparatus according to claim 1,wherein said bead is formed with rods between which an edge of a filtercloth is received, and secured by welding, and is of a softer materialthan said elongate member.
 12. A filtration apparatus which comprises aplurality of filtration sections, each said section covered by a filtercloth, and each said filter cloth formed with an integral compressibleedge bead which is received in a corresponding groove in a member whichextends between said sections, each said groove having an orifice forreception of said edge beads and said orifice being less than a diameterof said groove, and said member having a hollow core to receive a sectordividing stem.
 13. The filtration apparatus according to claim 12,wherein each said groove having lips of a flexible material for enablingsaid edge beads to be pushed into and pulled from said groove.
 14. Thefiltration apparatus according to claim 12, wherein said edge bead oneach said filter cloth is an elastomeric extrusion for forcing into eachsaid groove.
 15. The filtration apparatus according to claim 12, whereinsaid edge bead is formed with flaps between which an edge of each saidfilter cloth is received, and secured by stitching, and is of a softermaterial than said elongate member.
 16. The filtration apparatusaccording to claim 12, wherein said edge bead is formed with flapsbetween which an edge of each said filter cloth is received, and securedby welding, and is of a softer material than said elongate member. 17.The filtration apparatus according to claim 12, wherein said edge beadis formed with rods between which an edge of each said filter cloth isreceived, and secured by welding, and is of a softer material than saidelongate member.
 18. The filtration apparatus according to claim 12,wherein each said groove are of circular cross section and are set toform an orifice which is less than a diameter of said groove.
 19. Thefiltration apparatus according to claim 12, wherein said membercomprises an extrusion of a profiled cross section of a lightweightmetal, and has two grooves provided at each side of said member toreceive said bead edges, and said edge beads carried thereby, of twofilter cloths, one on each face, of each of said filtration sectionabutting said elongate member.
 20. The filtration apparatus according toclaim 12, wherein said edge bead on each filter cloth edge is anelastomeric extrusion which can be deformed for pushing in and pullingout from the groove.